Hmm, tough one really.
HTC Camera's are not much better than the ones motorola sticks in them to be honest! The droid has crapware on it and the HTC comes with stock sense.
It seems the processor performance is near identical, in real world application use atleast so thats a non-issue i.e. when one beomces outdated, so will the other.
In terms of mod community, the HTC phone is likely to get much more support on this website, simply because the majority of people here are HTC users or past HTC users.
The Milestone seems a bit more manly, rough and the HTC looks more refined IMHO.
Personally, I'd go the G2 if I wanted as much modding as possible. HTC has a much more open policy on the topic and no locked bootloaders (efuse etc).
At the end of the day, its your decision
Have a play with both phones and pick the one you feel looks better. A good question to ask is:
I know they both look nice now, but which one will look worse for wear (paint peeling, scratching etc)